The present invention relates generally to annular seal assemblies for effecting a seal between relatively movable parts. More particularly, the present invention relates to a seal element for an annular dove-tail groove that positions the mold flashing or parting lines on the seal element away from a sealed fluid, and that prevents unwanted toroidal rotation of the seal element.
Providing a seal between adjacent annular surfaces such as a piston and a surrounding cylinder and a plugging member and a surrounding housing is generally well known in the art. Such a seal is usually accomplished by employing a seal element formed from a relatively resilient, deformable sealing material, such as synthetic or natural rubber. The seal element is generally annular and often is generally circularly shaped in toroidal cross-section. The seal element is usually positioned in an annular groove or gland on either the central member or the surrounding member.
For certain applications, it is known to employ a groove that has a dove-tail shape in toroidal cross-section. As seen in FIGS. 1-3, such a dove-tail groove 10 typically has an opening or mouth 12, first and second side walls 14, 16, and an axial base wall 18 that extends between the side walls 14, 16. The dove-tail shape of the groove 10 is obtained by having the side walls 14, 16 extend toward each other as each side wall 14, 16, respectively, approaches the mouth 12 of the groove 10. Thus, each side wall 14, 16, is at an angle of less than 90 degrees with respect to the base wall 18. Also typically, at least one of the side walls 14, 16 meets the base wall 18 at a generally inwardly rounded surface 19.
It is well known to employ a seal element having a generally circular toroidal cross-section in connection with the dove-tail groove 10. Such a prior art seal element 20 is shown in FIG. 1, and is usually formed in a molding process. Accordingly, the prior art seal element 20 generally has a pair of mold flashing or parting points 22a, 22b generally oppositely situated on the surface 24 thereof at the point where the two halves of the mold met. Due to the nature of the molding process, one of the mold flashing points 22a naturally resides on a part of the surface 24 external to the groove 10 and in direct contact with a sealed fluid (not shown in FIG. 1).
While the prior art seal element 20 seen in FIG. 1 may be constructed and dimensioned to provided effective sealing, certain sealed fluids have been known to degrade the prior art seal element 20 at the points 22a, 22b and cause the prior art seal element 20 to fail. Such sealed fluids include several different plasmas (combinations of processing gases) employed in semiconductor processing applications, for example.
Further, due to the generally circular toroidal cross-section of the prior art seal element 20, the installation and operation of the prior art seal element 20 can result in toroidal rotational movement thereof. Such toroidal rotational movement causes improper seating of and unwanted internal stress within the prior art seal element 20. As a result, the toroidal rotational movement causes undue wear and failure of the prior art seal element 20.
The present invention comprises a seal element for installation in an annular dove-tail-shaped groove in which the seal element is positioned to avoid contact between mold flashing points thereon and a sealed fluid. Additionally, the seal element of the present invention has a toroidal cross-sectional shape that prevents toroidal rotational movement during installation and operation.